Black Box RS-485 Manual De Usuario

DUAL PORT RS-232↔422/485 SERIAL INTERFACE

The Dual Port RS-232/422/485 Serial Interface utilizes the same 16550 UART
chip found in the IBM

®

asynchronous adapter. This chip features

programmable baud rate, data format, and interrupt control. Refer to the
IBM Technical Reference for details on programming the chip. 

RS-232
The Dual Port RS-232/422/485 Serial Interface meets the RS-232C
specifications and provides an asynchronous serial I/O port. This is the
standard port configuration found in the IBM AT

®

computer, including the

DB9 style connector.

The table below shows the connector pinouts for ports J1 (port 1) and J2
(port 2) on the Interface while using RS-232.

3

Transmit Data (TD)

Output RS-232

7

Request To Send (RTS)

Output RS-232

4

Data Term Ready (DTR)

Output RS-232

5

Ground (GND)

––––––––––––

2

Receive Data (RD)

Input RS-232

1

Data Carrier Detect (DCD)

Input RS-232

6

Data Set Ready (DSR)

Input RS-232

8

Clear To Send (CTS)

Input RS-232

9

Ring Indicator (RI)

Input RS-232

RS-422
RS-422 allows very long distance communications—4000 feet (about
1219 meters) at 9600 baud—based on use of Category 3, UTP, or better, with
virtually error-free differential drive characteristics. RS-422 signal levels are
the standard electrical specification used in RS-449 and EIA-530. This allows
interfacing with equipment that meets these specifications.